While the principle of utilizing air pressure to support and guide a load as it moves along a track is not new, improvements in load-carrying efficiency have been achieved through the implementation of a system using rail sections having a concavely curved upper surface and by providing load supporting members which have a convexly curved compliant outer surface for mating with the rail surface. Nozzles leading from an air plenum within the rail through the upper wall exit at the curved upper surface thereof and are angled with respect to three ortogonal planes, one of which is tangent to the rail surface where the nozzle axis intersects that surface. The nozzles are angled so that their net effect is a fluid film wedge reaction on the load supporting member which directs it in the desired direction and which also tends to displace the load and the supporting film wedge towards one side of the rail. The principles outlined in very basic terms above are applicable to material handling systems, as in single-rail systems operating as an air-conveyor for trans-porting cyclindrical objects such as paper rolls, or in twin-rail track systems for transporting pallets from a loading or unloading dock into or out of a transport trailer, or holding and feeding pallets in and through a gravity flow racking system, and they are also applicable to so-called "people-movers" such as inter-or intra-urban transportation systems. The principles underlying the systems briefly outlined above are covered in one or more Canadian patents including Canadian Pat. Nos. 950,853 issued July 9, 1974 for "Air Conveyor"; 1,002,565 issued Dec. 28, 1968 for "Vehicular Transportation System"; and 1,066,645 issued Nov. 20, 1979 for "Air Film Supported and Guided Load Support Member".
In general, systems such as those described in the aforementioned patents may be broadly characterized as compliant hydrostatic bearing levitation systems for moving heavy loads along supporting rails. The systems utilize "shoes" of cellulose or like material wound tightly about a collapsible core and enclosed by a deformable but stiff cover of flexible plastic or metal, which shoes exhibit low friction properties when in juxtaposition with a trough-like section of support rail, curved at a radius only slightly greater than that of the shoe. The shoes move freely in the rail(s) when small nozzles in the curved rail surface exhaust fluid therethrough under pressure in particular patterns to create fluid cavity cells and fluid lubricated seal areas under the shoes, the shoes being guided by the fluid film wedge formed with the curved contour of the rail section.
While the structures which utilize the air film technology described in the aforementioned patents have proven to be very effective, further research into the operating theory and the real-life requirement of producing a product at a marketable cost has resulted in significant improvements, especially with respect to the rail configuration. Included in the portions requiring improvement were: the rail cross-section, including the arc of the curved upper surface; the manner in which the nozzles are produced, including the size, location and number required for optimum air flow rates and power usages; the control mechanisms for fluid flow (activation and deactivation) to the nozzles; the manner in which rails could be joined end-to-end without pressure loss and without any rail rigidity loss or any appreciable misalignment (essentially on a microscopic scale due to the thin-film fluid bearing created at the interface between the load and the rail upper surface); and the provision of auxiliary devices such as timers, valves, controls, pulse-pressure mechanisms, resonating cavities and linear motors for powering large-scale loads such as containers or "vehicles" per se.